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Biomedical subjects

X Yang

Publications and source records attributed to X Yang.

At least 847 records · Page 47Linked to original sources
PubMed1996

Absence of mutagenic effects of sodium dichloroacetate.

Sodium dichloroacetate (DCA) is a drug with potential for treating patients with stroke and head injury. Conflicting evidence has been published on the mutagenic potential of DCA. A series of genetic tests for mutagenicity and clastogenicity was carried out on pharmaceutical grade DCA. Four types of mutagenicity test were included, with and without metabolic activation where appropriate. These studies included: (i) Salmonella and Escherichia coli mutation (Ames) test, (ii) thymidine kinase locus forward mutation in L5178Y mouse lymphoma cells, (iii) tests for chromosomal aberrations in Chinese hamster ovary cells, and (iv) and in vivo rat bone marrow erythroid micronucleus test. In each study, there was no evidence of mutagenic activity attributable to DCA. It is possible that the present test material, of pharmaceutical grade, has fewer impurities than materials studied in previous reports. These data extend, and in some cases contradict, previous published reports on DCA.

Animals↗
PubMed1996

Enalaprilat, an angiotensin-converting enzyme inhibitor, enhances functional preservation during long-term cardiac preservation. Possible involvement of bradykinin and PKC.

We investigated the effect of enalaprilat (ET) on long-term preservation of cardiac explant. Isolated rat hearts (n = 7/group) were pretreated with 0 to 40 nM ET and stored at 0 degree C for 16 h. Functional viability was assessed after 30-min working reperfusion without ET. Prestorage control function (mean +/- S.E.M.) (n = 7) included heart rate (HR), 291 +/- 12 bpm; aortic flow (AF). 49.8 +/- 1.9 ml/min; coronary flow (CF), 25.2 +/- 1.3 ml/min; cardiac output (CO), 75.0 +/- 1.2 ml/min; and work, 89.4 +/- 4.7 g-m/min. Post-storage function of untreated hearts was: AF, 61%; CF, 43%; CO, 55%; work, 48% of control. ET (20 nM) enhanced AF recovery to 85%; CF, 58%; CO, 76%; work, 73% of control (P < 0.05 v untreated). Hoe 140 (D-Arg-[Hyp2, Thi5,8, D-Phe7]BK) (1 nM) a bradykinin receptor antagonist, inhibited ET effect; function returned to the untreated level. Protein kinase C (PKC) inhibitors staurosporine (15 nM) and bisindolylmaleimide I (0.5 microM) also blocked ET effect. After 4 h of cold storage, membrane PKC activity changed little from the prestorage level in the untreated hearts, but was elevated significantly from 52.8 +/- 5.2 pmol/min/mg to 74.7 +/- 8.2 by 20 nM ET (P < 0.05 v untreated). Cytosol PKC did not change during 4 h cold storage with or without ET. Neither end-storage nor end-reperfusion myocardial ATP content was affected by 20 nM ET treatment. In conclusion, ET improves cardiac preservation possibly via bradykinin receptor and PKC without affecting ATP metabolism.

Adenosine Triphosphate↗
PubMed1996

Focal adhesion kinase as a marker of invasive potential in differentiated human thyroid cancer.

BACKGROUND: The FAK gene encodes a 125-kDa tyrosine kinase (p125FAK) involved in signal transduction pathways used in cell adhesion, motility, and anchorage-independent growth. Because thyroid carcinomas have a wide variability in their propensity for invasion and metastasis, we studied the expression of FAK in a variety of thyroid tissues. METHODS: We synthesized a recombinant N-terminal fragment of the human FAK protein and developed a specific polyclonal antisera. Using Western blot analysis, we assessed the levels of p125FAK expression in 30 human thyroid tissue samples from 27 patients that included paired normal and malignant specimens. Levels of FAK protein in individual tumors were quantitated by densitometric scanning of the immunoblots, and the results were correlated with tumor histology and biologic behavior. RESULTS: The levels of FAK expression were directly correlated with thyroid carcinomas demonstrating the most aggressive phenotypes. The highest levels of p125FAK were seen in follicular carcinomas and tumors associated with distant metastatic foci. In contrast, neoplastic thyroid tissues with limited invasive potential, such as papillary carcinomas, follicular adenomas, and other nonmalignant thyroid lesions, showed minimal p125FAX expression. CONCLUSIONS: Overexpression of FAK may be part of a mechanism for invasion and metastasis of thyroid cancer. Furthermore, the levels of p125FAK may serve as a marker of biologic behavior in this disease.

Adenocarcinoma, Follicular↗
PubMed1996

Application of whole-mount section of lung specimen in study of radiologic-pathologic correlations.

We evaluated the usefulness of the whole-mount section of the inflated-fixed lung specimen in the study of radiologic-pathologic correlations. Altogether, 24 resected fresh lobe specimens with 1.5- to 3.0-cm solitary pulmonary carcinomas or tuberculomas were inflated with air, intrabronchially fixed by infusing Heitzman's solution, and finally cut into 10- to 15-micron-thick whole-mount sections for the histopathological examination. All 24 inflated-fixed lobes were satisfactorily soft as sponge, sufficiently springy, and kept their original shape. All whole-mount sections clearly presented the complete morphological features of the whole lobes, and could be directly observed by the naked eye and examined under microscopy. The use of the whole-mount section of the lung specimen may facilitate precisely and effectively the studies of the radiologic-pathologic correlations.

Adenocarcinoma↗
PubMed1996

Mutations in masquerade, a novel serine-protease-like molecule, affect axonal guidance and taste behavior in Drosophila.

The masquerade (mas) locus encodes an extracellular molecule with a striking similarity to serine proteases. The serine residue, which is essential for enzymatic activity, has been substituted by glycine, suggesting that MAS could serve to antagonize serine protease activity [Murugasu-Oei et al. (1995), Genes Dev. 9, 139-154]. We describe the expression pattern of mas mRNA and protein in the developing embryonic, larval and pupal nervous system and in the epidermis. Total loss of mas function is lethal and results in aberrations in the embryonic central and peripheral nervous systems, consistent with a role in axonal guidance. The possibility that the observed deficits in taste behavior, exhibited by animals with partial loss of mas function, are a result of defects in the adult brain are discussed.

Animals↗
PubMed1996

Molecular diffusion into horse spleen ferritin: a nitroxide radical spin probe study.

Electron paramagnetic resonance spectroscopy and gel permeation chromatography were employed to study the molecular diffusion of a number of small nitroxide spin probes (approximately 7-9 A diameter) into the central cavity of the iron-storage protein ferritin. Charge and polarity of these radicals play a critical role in the diffusion process. The negatively charged radical 4-carboxy-2,2,6,6-tetramethylpiperidine-N-oxyl (4-carboxy-TEMPO) does not penetrate the cavity whereas the positively charged 4-amino-TEMPO and 3-(aminomethyl)-proxyl radical and polar 4-hydroxy-TEMPO radical do. Unlike the others, the apolar TEMPO radical does not enter the cavity but instead binds to ferritin, presumably at a hydrophobic region of the protein. The kinetic data indicate that diffusion is not purely passive, the driving force coming not only from the concentration gradient between the inside and outside of the protein but also from charge interactions between the diffusant and the protein. A model for diffusion is derived that describes the observed kinetics. First-order half-lives for diffusion into the protein of 21-26 min are observed, suggesting that reductant molecules with diameters considerably larger than approximately 9 A would probably enter the protein cavity too slowly to mobilize iron efficiently by direct interaction with the mineral core.

Animals↗
PubMed1996

Pulmonary parenchymal manifestations surrounding small peripheral masses: pathologic correlation with chest radiographs and diagnostic value.

RATIONALE AND OBJECTIVES: We evaluated pathologic correlations of pulmonary parenchymal manifestations surrounding small peripheral masses and their usefulness in differentiating small peripheral bronchogenic carcinomas from tuberculomas. METHODS: We evaluated 29 resected lobe specimens with 1.5- to 3.5-cm solitary pulmonary masses, including 24 carcinomas and five tuberculomas. These specimens were prospectively studied with preoperative chest radiographs, postoperative specimen radiographs, 10- to 15-microns-thick wholemount sections, and 5-microns-thick slices. A total of 100 chest X-rays and conventional tomography scans of 1- to 3-cm peripheral pulmonary masses, including 60 carcinomas and 40 tuberculomas, were retrospectively reviewed and analyzed. RESULTS: The pulmonary parenchymal manifestations surrounding the masses presented as small infiltrates and nodular protrusions, thickened strands, and "double track" shadows, which extended from the proximal margin of five tuberculomas (100%, 5 of 5) and from the distal margin of 17 carcinomas (71%, 17 of 24). These pulmonary changes represented caseous material spreading from tuberculomas into the proximal bronchus and alveolar inflammatory exudation distal to the carcinomas. The proximal pulmonary manifestations were significantly more frequent in tuberculomas than in carcinomas (p < .01), whereas the distal pulmonary manifestations were more often found in carcinomas than in tuberculomas (p < .01). CONCLUSION: The radiologic findings of the pulmonary parenchymal manifestations proximal or distal to the masses may be valuable radiologic signs for distinguishing between tuberculomas and small peripheral bronchogenic carcinomas, even though there is still considerable crossover between the two disease populations in the findings.

Carcinoma, Bronchogenic↗
PubMed1996

Proteinases in renal cell death.

The role of proteinases in renal proximal tubule (RPT) cellular death was examined using specific inhibitors of proteinases. Rabbit RPT suspensions were incubated with antimycin A for 1 h or tetrafluoroethyl-L-cysteine (TFEC) for 4 h in the absence or presence of the specific cysteine proteinase inhibitor L-trans-epoxysuccinyl-leucylamido (4-guanidino)butane (E-64), the serine proteinase inhibitors N-p-tosyl-L-lysine chloromethyl ketone (TLCK) or 3,4-dichloroisocoumarin (DCS), the serine and cysteine proteinase inhibitors leupeptin or antipain, or the aspartic proteinase inhibitor pepstatin. E-64 and pepstatin decreased lactate dehydrogenase (LDH) release, a marker of cell death, from RPT exposed either to antimycin A or TFEC. TLCK, DCS, leupeptin, or antipain did not decrease antimycin A- or TFEC-induced cell death. Bromohydroquinone- or t-butylhydroperoxide-induced cell death was not decreased by any of the proteinase inhibitors. Loss of lysosomal membrane potential, indicated by neutral red release, occurred prior to the onset of antimycin A-induced cell death. Extensive inhibition of lysosomal cathepsins B and L by E-64 was correlated with cytoprotection. However, E-64 was only protective after some cell death had occurred. These results suggest that lysosomal cysteine and aspartic proteinases, but not serine proteinases, play a role in RPT cell death induced by antimycin A or TFEC. The observation that E-64 was only protective after some cell death had occurred suggests that lysosomal cathepsins are released from dying cells and subsequently attack the remaining viable cells.

Animals↗
PubMed1996

Identification of two novel cellular genes associated with multistage carcinogenesis of human endocervical cells by mRNA differential display.

Carcinogenesis originating from cervical cells has been recognized as a multistage process in which human papillomavirus (HPV) infection and cofactors, such as cigarette smoke, are frequently involved in the development of malignant cancer. However, the molecular mechanism underlying this process remains poorly understood. To identify the cellular genes involved in multistage cervical oncogenesis, we used the mRNA differential display method to analyze primary human endocervical cells (HEN), HPV 16-immortalized cells (HEN-16) and cigarette smoke condensate (CSC)-transformed cells (HEN-16T). Two cDNAs--PA4 and PA9--have been identified and isolated after comparing 8000 cDNAs from HEN, HEN-16 and HEN-16T. Northern blot analysis showed that PA4 was expressed 2- to 3-fold higher in HEN-16 and HEN-16T than in HEN, whereas PA9 was expressed uniquely in HEN. Moreover, the same patterns of PA4 and PA9 expression were found for a second line of HPV 16-immortalized endocervical cells and the corresponding transformed cells. An analysis of cDNA sequences showed that PA4 and PA9 had no homology to nucleotide sequences in Genbank. We suggest that immortalization, but not tumorigenesis, up-regulated a new oncogene, PA4, and down-regulated a new tumor suppressor gene, PA9. These results demonstrated the utility of the human endocervical cell model system and the mRNA differential display method for identifying the genes that may be involved in multistage cervical carcinogenesis.

Base Sequence↗
PubMed1996

Malignant transformation of human ectocervical cells immortalized by HPV 18: in vitro model of carcinogenesis by cigarette smoke.

In addition to the established role of human papillomaviruses (HPVs) in cervical cancer, smoking has been suggested to be an important cofactor. Previously, primary human ectocervical cells immortalized by HPV types 16 and 18 DNA did not form tumors on nude mice. Here, we derived a new line of HPV 18-immortalized ectocervical cells (HEC-18-1), which was also non-tumorigenic. To examine the role of cigarette smoking in the progression of cervical cancer initiated by HPV 18, we adapted these cells to growth in serum and high calcium and treated the cells with cigarette smoke condensate until tumorigenic cells (HEC-18-1C) were produced. Moderate and late passage serum-adapted untreated HEC-18-1 (HEC-18-1S) remained non-tumorigenic. A typical HEC-18-1C tumor was an invasive squamous cell carcinoma, from which we established a clonal line of cells (HEC-18-1CT). Although the physical state of HPV 18 was not affected by malignant transformation and the gene expression of HPV 18 was not affected by malignant transformation and the gene expression of HPV 18 was affected little, the differentiation of the epithelium derived in organotypic (raft) culture from HEC-18-1CT was altered dramatically. Moderate and late passage HEC-18-1 and HEC-18-1S were reconstructed into mild dysplasia in organotypic (raft) culture. On the other hand, the moderate passage malignantly transformed HEC-18-1CT displayed severe dysplasia/carcinoma in situ in raft culture. We describe here the first direct evidence of the role of cigarette smoke in the progression of HPV-initiated carcinogenesis using an in vitro model system.

Animals↗
PubMed1996

Oxidized low density lipoproteins alter macrophage lipid uptake, apoptosis, viability and nitric oxide synthesis.

Uptake of oxidized low density lipoproteins (LDL) by monocyte macrophages to form "foam" cells occurs during formation of atherosclerotic lesions. Inducible nitric oxide synthase (iNOS) has been identified in foam cells. To investigate interactions between oxidized LDL, monocyte macrophage viability and iNOS, studies were performed with J774.Al macrophages. iNOS mRNA, protein and enzyme activity were induced in J774.Al macrophages by IFN-gamma lipopolysaccharide (LPS). Neither iNOS induction nor inhibition of nitric oxide (NO) formation was associated with significant alterations in the binding, uptake or degradation of native or oxidized LDL. Nontoxic doses of native LDL or of oxidized LDL did not influence iNOS mRNA or protein in macrophages. However, oxidized LDL, but not native LDL or acetyl LDL, inhibited NO production by macrophages in a dose- and time-dependent fashion. Inhibition of iNOS was not correlated with cholesteryl ester formation but with the degree of LDL oxidation. Inhibition of iNOS did not require the scavenger receptor or directed endocytosis and exhibited noncompetitive kinetics. Inhibition of iNOS activity in J774.Al macrophages was produced by lipid from oxidized LDL but not by lipid from native LDL and by PC vesicles containing LPC but not by PC vesicles alone. Inhibition of NO formation diminished apoptosis of the activated macrophages. The data suggest NO production by iNOS and inhibition of the enzyme by oxidized LDL lipid may influence cell viability, cell-cell interactions and vasomotor tone during atherogenesis.

Animals↗
PubMed1996

Vascular manifestations of small solitary pulmonary masses. Angiographic-pathologic correlations and clinical significance.

RATIONALE AND OBJECTIVES: By performing pulmonary specimen angiographies, the authors attempted to determine the pathologic correlations of the vascular-related radiologic manifestations within, at the edge of, and adjacent to the small solitary pulmonary masses, and to evaluate their usefulness in differentiating small bronchogenic carcinomas from tuberculomas. METHODS: A total of 29 resected lobe specimens with 1.5- to 3.5-cm solitary pulmonary masses, including 24 carcinomas and 5 tuberculomas, were studied prospectively with preoperative radiographs, postoperative specimen arteriographies (in 19 carcinomas and 5 tuberculomas), and venographies (in 5 carcinomas), 10- to 15 micrograms-thick whole-mount sections, and 5-micrograms-thick slices for the examination of angiographic-pathologic correlation. Another series of chest radiographs and conventional tomographs of 100 patients with 1- to 3-cm peripheral pulmonary masses, including 60 carcinomas and 40 tuberculomas, were reviewed retrospectively and analyzed with the chi-square test. RESULTS: Specimen angiographies showed the intralesion avascularity, small arterial speculation, and lobulation or notch at the mass margin with arterial compression, as well as vascular convergence to the mass, in both carcinoma and tuberculoma groups. The irregular arterial wall (79.2%) and venous dilation distal to the mass (100%) were found in the carcinoma group only. Microscopically, arterial or venous fibrous hyperplasia was observed in both carcinomas and tuberculomas, whereas the arterial erosion by tumor tissue and tumor emboli within the vessels were found in carcinomas only. The retrospective review of the 100 patients showed that two radiologic signs of the vascular convergence to the mass and the vascular dilation distal to the mass occurred at similar frequencies (12%-13%) between the carcinoma and tuberculoma groups. CONCLUSIONS: In addition to compression of vessels by tumor and vessel occlusion by tumor embolus, pulmonary vascular fibrotic hyperplasia can cause intramass avascularity. Small vessels running vertically into or from the mass margin can construct the spiculation sign of the tuberculomas. Any evidence of pulmonary vascular irregularity will indicate a bronchogenic carcinoma. The vascular convergence to the mass and the vascular dilation distal to the mass are not specific radiologic signs for small solitary bronchogenic carcinomas.

Adenocarcinoma↗
PubMed1996

Stability of habitual physical activity and sport participation: a longitudinal tracking study.

Although one of the most important aims of physical education and public sport policy is to encourage life-long habitual physical activity, very little is known of the stability or tracking of physical activity. As a part of a larger research project called Cardiovascular Risks in Young Finns, the purpose of the study reported here was to investigate the stability (tracking) of leisure-time physical activity and sport participation at intervals of 3, 6, 9 and 12 years from age 9 to 30. The subjects, chosen by stratified random sample, represent five geographical areas of the country and eight gender-age cohorts (9, 12, 15 and 18 years old in 1980). Physical activity and sport participation were measured using a short questionnaire. Tracking was analysed by Spearman's rank order correlations and by simplex model. The tracking correlations within a 3-year interval of all individual variables were significant but rather low. The tracking correlations of the sum index of physical activity comprising five variables varied from 0.50 to 0.80 among boys and from 0.40 to 0.61 among girls. Simplex models that fitted the data very well showed higher stability coefficients than rank order correlations. With one exception the correlations of physical activity index within the 12-year interval were significant but low.

Adolescent↗
PubMed1996

Surveying a supercoil domain by using the gamma delta resolution system in Salmonella typhimurium.

A genetic system was developed to investigate the supercoil structure of bacterial chromosomes. New res-carrying transposons were derived from MudI1734 (MudJr1 and MudJr2) and Tn10 (Tn10dGn). The MudJr1 and MudJr2 elements each have a res site in opposite orientation so that when paired with a Tn10dGn element in the same chromosome, one MudJr res site will be ordered as a direct repeat. Deletion formation was studied in a nonessential region (approximately 100 kb) that extends from the his operon through the cob operon. Strains with a MudJr insertion in the cobT gene at the 5' end of the cob operon plus a Tn10dGn insertion positioned either clockwise or counterclockwise from cobT were exposed to a burst of RES protein. Following a pulse of resolvase expression, deletion formation was monitored by scoring the loss of the Lac+ phenotype or by loss of tetracycline resistance. In exponentially growing populations, deletion products appeared quickly in some cells (in 10 min) but also occurred more than an hour after RES induction. The frequency of deletion (y) diminished with increasing distance (x) between res sites. Results from 15 deletion intervals fit the exponential equation y = 120 . 10(-0.02x). We found that res sites can be plectonemically interwound over long distances ( > 100 kb) and that barriers to supercoil diffusion are placed stochastically within the 43- to 45-min region of the chromosome.

Cell Division↗
PubMed1996

Homologous pairs of regulatory proteins control activity of Bacillus subtilis transcription factor sigma(b) in response to environmental stress.

In Bacillus subtilis, activity of the general stress transcription factor sigma B is controlled posttranslationally by a regulatory network that transmits signals of environmental and metabolic stress. These signals include heat, ethanol, or osmotic challenge, or a sharp decrease in cellular energy levels, and all ultimately control sigma B activity by influencing the binding decision of the RsbW anti-sigma factor. In the absence of stress, RsbW binds to sigma B and prevents its association with RNA polymerase core enzyme. However, following stress, RsbW binds instead to the RsbV anti-anti-sigma factor, thereby releasing sigma B to direct transcription of its target genes. These two principal regulators of sigmaB activity are encoded in the eight-gene sigB operon, which has the gene order rsbR-rsbS-rsbT-rsbU-rsbV-rsbW-sig B-rsbX (where rsb stands for regulator of sigma B). Notably, the predicted rsbS product has significant amino acid identity to the RsbV anti-anti-sigma factor and the predicted rsbT product resembles the RsbW anti-sigma factor. To determine the roles of rsbS and rsbT, null or missense mutations were constructed in the chromosomal copies or each and tested for their effects on expression of a sigma B-dependent reporter fusion. On the basis of this genetic analysis, our principal conclusions are that (i) the rsbS product is a negative regulator of or" activity, (ii) the rsbT product is a positive regulator, (iii) RsbS requires RsbT for function, and (iv) the RsbS-RsbT and RsbV-RsbW pairs act hierarchically by a common mechanism in which key protein-protein interactions are controlled by phosphorylation events.

Amino Acid Sequence↗
PubMed1996

The human immunodeficiency virus Tat proteins specifically associate with TAK in vivo and require the carboxyl-terminal domain of RNA polymerase II for function.

Human immunodeficiency virus types 1 and 2 encode closely related proteins, Tat-1 and Tat-2, that stimulate viral transcription. Previously, we showed that the activation domains of these proteins specifically interact in vitro with a cellular protein kinase named TAK. In vitro, TAK phosphorylates the Tat-2 but not the Tat-1 protein, a 42-kDa polypeptide of unknown identity, and the carboxyl-terminal domain (CTD) of RNA polymerase II (RNAP II). We now show that the 42-kDa substrate of TAK cochromatographs with TAK activity, suggesting that this 42-kDa polypeptide is a subunit of TAK. We also show that the Tat proteins specifically associate with TAK in vivo, since wild-type Tat-1 and Tat-2 proteins expressed in mammalian cells, but not mutant Tat proteins containing a nonfunctional activation domain, can be coimmunoprecipitated with TAK. We also mapped the in vivo phosphorylation sites of Tat-2 to the carboxyl terminus of the protein, but analysis of proteins with mutations at these sites suggests that phosphorylation is not essential for Tat-2 transactivation function. We further investigated whether the CTD of RNAP II is required for Tat function in vivo. Using plasmid constructs that express an alpha-amanitin-resistant RNAP II subunit with a truncated or full-length CTD, we found that an intact CTD is required for Tat function. These observations strengthen the proposal that the mechanism of action of Tat involves the recruitment or activation of TAK, resulting in activated transcription through phosphorylation of the CTD.

Animals↗